Using oxalic acid as a standard for chemical oxygen demand determination with closed reflux–colorimetric method
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nhu cầu oxi hóa học, COD, kali hydro phthalate, KHP, axit oxalic nhu cầu oxi hóa học
kali hydro phthalate
axit oxalic
chemical oxygen demand

How to Cite

Long HT, Bảo NS, Dung TTK. Using oxalic acid as a standard for chemical oxygen demand determination with closed reflux–colorimetric method. hueuni-jns [Internet]. 2021Jul.5 [cited 2021Oct.23];130(1C):23-30. Available from:


Potassium hydrogen phthalate (KHP) is used as a standard to determine the chemical oxygen demand (COD) with the closed reflux-colourimetric method (colourimetric method). Besides KHP, it is possible to utilize oxalic acid for this purpose. After boiling at 150 °C for more than 30 minutes in H2SO4 containing Ag2SO4, K2Cr2O7 reacts completely with H2C2O4 at a molar ratio of 1:3. The experimentally determined chemical oxygen demand of H2C2O4 coincides with its theoretical value at 16.0 mg O2/mole H2C2O4. The average COD values of two river water samples, determined with the colourimetric method by using KHP standard and oxalic acid, are not statistically different. Oxalic acid can be used as a standard to determine COD with the colourimetric method.
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